Method for the distillation of petroleum



May 19, 1931. E. G. RAGATZ 1,806,023

METHOD IJR THE DI STILLATION OF PETROLEUM Filed Nov. 6, 1926 2 Sheets-Sheet l May l9, 1931. E. G. RAGATZ METHOD FOR THE DISTILLATION OF PETROLEUM 6, 1926 2 Sheets-Sheet 2 Filed Nov.

444 ATTORNEY I Patented May 19, 1931 flUNITflED STATES PATENT OFFICE EDWABD- G. RAGATL OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO UNION OIL COM- PANY CALIFORNIA, OF LOS ANGELES, CALIFORNIA, A CORPORATION OF GALI- FORNIA mnrnon FOR THE DISTILLATION. on PETROLEUM Application filed November 6, 1926.' Serial No. 146,67

The invention relates to methods and apparatus for distilling and fractionating petro-.. leum feed material (either crude or partially rectified) into a residual or heavy cut and one ormore overhead or light cuts, the terms heavy and light being used in a relative sense only. The primary object of the inven-' tion is to obtain all such cuts in forms sharply defined from one another,- the method and 10 apparatus being adapted to the production of successive sharp cuts from the original feed stock in successive units of apparatus wherein the residual cut from one unit is further sharply cut in another unit of substantially the same type. lVith this process, the distillation and separation of the original feed material is efl'ected in sucha manner thatv the initial vaporization temperature of the residual cut, as determined by a standard Engler distillation apparatus, is equal to or greater than the maximum Engler distillation temperature of the heaviest overhead cut, indicat-" ing a maximum yield of overhead material. The entire operation is carried out at temperatures low enough to effectively suppress any tendency towards cracking on the part of either the original feed material or its distillation products. 7

Briefly outlined, the invention comprises 1. The initial heating of a feed material to at least that minimum temperature necessary for the efiective operation of the process, this temperature usually approximating the temperature of the-vapors in a distilling column at the point Where the feed material is introduced.

' 2. The introduction of this heated feed material onto a feed plate of said column wherein the vapors formed during the initial heating operation are released, and wherein the hot remaining liquid is subsequently brought into intimate contact with a countercurrent-ly flowing stream of hotter vapors in a portion of the column referred to as an exhausting section. I

- 3. The removal, as a result of the aforementioned intimate contact maintained between counter-currently flowing streams of cooler liquid and hotter vapors, of most of the desired overhead'material content of the liquid portion of the feed.

4. The extraction of the denuded, orv exhausted, liquid from the aforementioned column and its subsequent heating in an exhausting heater (preferably tubular) to a temperature sufl'icient to furnish the hot recycling vapors required for the aforementioned exhausting operation; this heating also serving to vaporize the last of the overhead-l, material content of the exhausted liquid. 5. The separation, in an exhausting vapor separator .apart from the heating elements 'of the exhausting heater, of the aforementioned exhausting vapors, and their subsequent introduction into the exhausting section of the aforementioned column.

6. The extraction of the remaining liquid from the exhausting vapor separator to form the desired residualorheavy out.

7. Theintroduction of the vapors arising from the aforementioned feed plate into a washing and fractionating .section wherein these vapors are brought into intimate counter current contact with a colder liquid reflux material for the purpose of removing the undesirable heavy fractions entrained and vaporized at the aforementioned feed plate.

8." The introduction, in case several overlapping overhead cuts are desired, of the initially fractionated vapors into an additional fractionating section wherein they are separated and condensed to form the desired overlapping light material cuts by being brought into intimate counter-current contact with a still colder liquid refiux' material.

9. The maintenance of a minimum amount of-liquid material in the system in order to make possible quick adjustments of control.

10. The introduction of steam into any portion in the system, the carrying of a part or all of the system under a vacuum, or the combination use of steam and vacuum, for the purpose of lowering the temperatures under which the system operates; this lowering of temperature being for the purposeof improving the quality of the resultant products, for the suppression of cracking, or for both.

. It should be noted that the invention re-- sides not only in the points developed in the above outline, but also in all other novel features, steps or combinations thereof presented elsewhere in the disclosure.

In the accompanying drawings wherein certain embodiments of the invention are shown by way of illustration and wherein two' sets of apparatus suitable for the operation of the process are outlined,

Fig. 1 discloses diagrammatically an installation comprising two complete units;

Fig. 2 is a cross section taken on line 2-'2 of Fig. 1;

Fig. 3 is a cross section taken on line 33 of Fig. 1;

Fig. 4: discloses diagrammatically an installation comprising a single unit used in conjunction with fractionating apparatus suitable for the production of a plurality of overlapping overhead light cuts;

Fig. 5 is a cross section taken on the line 5-5 of Fig. 1;

Fig. 6 is a section taken on the line 6-6 of Fig. 5;

ig. 7 is a cross section taken on the line 77 of Fig. 4; and

Fig. 8 is a section taken on the line 8-8 of Fig. 2.

As illustrated, the feed stock is brought into the apparatus thru a line 1 by means of a pump P and conducted through heat exchanges 2 to a tubular feed heater 3, various pumps P being used throughout the system wherever required. From the feed heater 3, wherein the stock is heated to a predetermined degree, the feed is led by .a line 4 into a central portion of a distilling and rectifying column E wherein the said feed stock is' discharged onto a distributing or feed plate 5.

The feed heater 3 is controlled so as to produce a feed temperature, as determined by immediately above the feed plate, but in oper-' ating practice it is found advisable to heat the said feed 2 to 10 F. higher than these vapors in order to be sure that the optimum temperature has been reached. The temperature of these vapors may be determined by a thermometer 7 positioned well above-the feed plate 5 and so protected that it avoids being splashed by the entering feed stock.

At the feed plate 5 the vapor content of the heated feed stock is released and the remaining liquid uniformly distributed over the top of an exhausting section 8 containing spiral tile or the like. The feed then flows by gravity down thru the exhausting tile constituting the section 8, encountering and being brought into intimate contact with an ascending current of hotter vapors. This counter-current intimate contactof ascend ing hotter vapors with descending colder liquid feed results in the boiling out from the liquid of most of its desired light out fractions. Thus the exhausted stock, when it falls into the chamber 9 at the bottom of the column E, contains only a small amount of the heaviest of those fractions which ultimately go to make up the desired light material cuts.

From the chamber 9 the hot bottoms are Withdrawn by means of another pump P and forced through. the line 10 to a tubular exhausting heater H. At the heater H the hot denuded stock is forced through the heating coils 11, being mixed with superheated steam at the steam inlet connection 12. The heater H is fired to a temperature, as determined by the thermometer 13, sufiicient to free the stock of its remaining light material content and tofurnish the quantity of continuously recycling vapors required for the exhausting of successive increments of feed stock in the exhausting section 8, these vapors being continuously condensed and returned to heater H along with the denuded stock. The introduction of superheated steam at point 12 in the still coils makes it possible to avoid the cracking of the exhausted feed stock while vaporizing the required quantity of,

rated from. the liquid and from which they are conducted through the line 15 to the com- ,partme'nt 9 beneath the exhausting section in the column In the vapor separator S, the mixture of liquid and vapors is discharged onto the uppermost of a plurality of vaporizing trays 16, and in passing down over these trays, presents a large surface to thevapor space within the separator with the result that the vapors are readily separated from the liquid, yielding a residual material free from entrained vapor fractions. This residual material settles into compartment 17 at the base of separator S while the liberated Vapors pass upthrough annular spaces 18 between the vaporizing trays and the separator shell and thence to the line 15.

The hot residual liquid now free from vapors and light constituents is withdrawn from the base of the separator S through the line 19 and another pump P. This material constitutes the desired residual or heavy cut of the original feed stock, and may be passed either to storage by way of line 19 and heat exchanger 2, or by-pa'ssed throughvalve 19 to be subjected to further treatment in a second unit substantially like the one just described and comprising a preheater 3', an exseparator S, which areemployed to produce hausting column E, a heater H and a vapor of 1, receives-reflux from a superimposed recti ing or fractionating column B provided with a series of screen ,fractionating trays 21 equipped with suitable reflux downflow tubes 21; the lowermost tray being constructed to uniformly distribute said reflux over the top of the column of wash tile 20 whereby the heavier constituents of the rising vapors are washed out and returned to the exhausting section 8 by the counter-current scrubbing action of the descending reflux. The vapors which rise from the top tray of the fractionating column B are conducted by line 22 to a reflux condenser' 23 wherein the heavier portions are condensed and returned by line 24 to the top plate 21 of the section R. The desired light out from reflux condenser 23 is then passed by way of condenser C to a receiving tank T, which if desired may be placed under vacuum by means of vacuum pump V: In order to control the temperature and the rectifying conditions in section B the character and tempzrature of the reflux from condenser 23 may regulated by the introduction of a quantity of the light out from receiving tank T into the reflux line 24 by way of a line 25.-

The excess of the light cut is conducted from receiving tank T to the storage reservoir T.

According to the form of Fig. 4, vapors from the top of the wash section 20 in column E are passed by way of line 26 into a chamber 27 at the'bottom of a primary rectifying or fractionating column B which performs substantially the same function as column B. of Fig. 1. At the same time the bottoms from said column B, are picked up by a pump P from the chamber 27 and conducted through a line 28 to a distributor plate located above the section 20 of wash tile. These fracvtionator bottoms are uniformly distributed over the top of the column of wash tile 20' by said distributor plate 20" and flow by gravity-down through the wash column, encountering and being brought into intimate contact with the aforementioned ascending Wash column 20 thf'ough the line 26 to the compartment 27 contain undesirable heavyfractions which were vaporized within the ex- '-hausting column E and which are to be removed in the rectifying column R. This latter column is composed of aplurality of screen bottomed fractionating trays 29 provided with suitable reflux downflow tubes 29, like trays 21 and tubes 21. The ascending vapors within this column enter succeeding trays through the screen bottoms and intimately mix with the liquid held on these trays, while the descending refiux liquid gravitates from screen to screen via said reflux tubes. Reflux liquid for the operation of said column B is obtained from the compartment 30 in the base of a secondary fractionating column F and forced via the line 31 to the top screen of the primary fractionating column B. The intimate counter-current contact thus obtained between ascending vae pors and descending reflux liquid yields a vapor overhead at the top of the fractionating column R which is entirely freed of all undesirably heavy fractions. These vapors are thenconducted via the line 32 to the compartment 30 preparatory to being separated and condensed into the desired overhead, or light, cuts. The quality of the overhead va pors from primary fractionator R is maintained by controlling the quantity of reflux pumped into the column B to yield a constant predetermined vapor temperature as indicated by the thermometer 32'.

Secondary fractionating column F is constructed similarly to primary column B with the exception that a bleeder tray 33 is added at a predetermined intermediate point within the column. The fractionated vapors from line 32 are introduced into the compartment 30 of this columnand again ascend through a downflowing stream of colder reflux. From this compartment 30 a portion of the liquid which collects therein is withdrawn for refluxing to column R as just described, while the remainder is withdrawn by a pump and forced through a line 34 via a cooler 35 to storage. This latter material constitutes the heaviest of the desired overhead, or light, cuts.

The bleeder tray 33. isso constructed that a suflicient level of liquid is carried on the tray to permit of drawing 05 a portion of the same via; the line 36, whence it is transferred through line 37 and cooler 38 to storage. This material constitutes the second heaviest of the desired overhead cuts; its quality being maintained by so regulating the rate of bleeding as to holda constant predetermined liquid temperature on the bled material as determined by the thermometer 39. v

The vapors leaving the top of the fractioner remaining oil vapors are led via a line 42 to the condenser 44 where they also are condensed and subsequently gravitated via a line 45 to drum 46. Reflux liquid is pumped via line 47 onto the top tray 48 of'fractionating column F to maintain the control on the vapors going to the partial condenser 41, as indicated by the thermometer 49, material from either drum 43 or 46 being used for this reflux, according to the character of the desired finished cuts. The quality of the vapors going to condenser 44 via line 42' is controlled by regulating the quantity of cooling material circulated through the partial condenser 41,,

this control being maintained by holding a constant predetermined temperature on the vapors in line 42 as indicated by the thermometer 50. Any water which accumulates in drums 43 or 46 is removed by suitable pumps, while the balance of the materials tial vacuum, this being maintained by the steam condenser 51 and the vacuum pump V which remove the uncondensed steam and fixed gases from the system via line 54.

Any or all of the cuts obtained as described above may be rerun through a similar apparatus for the production-of still sharper cut materials and with similar results, the temperatures being varied to suit the desired cuts.

Preparatory to taking up the operation of the process more in detail, it should be noted that the uniqueness of the invention resides at least partially in the following items:

1.' Heating the feed above a very definite lower temperature limit to obtain the desired sharp out between residual and overhead products; the amount of this necessary heating varying, of course,-with each feed mate'- rial and character of desired overhead products, as more fully developed hereinafter.

2. The use of a special type of exhausting heating unit in conjunction with a combination of exhausting and fractionating'column sections; this special exhausting heating unit consisting of an apparatus wherein the evolved vapors required for the exhausting operation are separated from the residual liquid in a separating element apart from the heating elements of the exhausting heater the residual liquid being subsequently removed from the system without its coming again into contact with the aforementioned exhausting heating elements. This facilitates if the desired sharp out between residual and overhead products is to 'be obtained.

4. The elimination of .the storage of any appreciable volumes of oil within the system,

whereby control adjustments may be quickly obtained.

In the exhausting column phase of the disclosed process, the original feed material must be denuded of a large proportion of its original light material content; the quantity re moved being such that the subsequent evolution of vapors at the exhausting vapor separator will eliminate from the residual liquid all of the remaining desired overhead fractions. The removal of this light material content within the exhausting column section occurs in two phases, namely, the initial releasing of the vapors formed by the feed heating operation, and the subsequent evolution and removal of additional vapors throu h the intimate contact obtained between tie liquid feed material and the hotter counter-current- 1y flowing stream of recycling exhausting vapors. The effective operation of the process depends upon the correct balancing of these two vapor releasing phases; if the feed material is heated too much, too heavy vapors will be released at the feed plate, and an excess amount of refluxing will be required at the rectifying columns; if the feed material is heated too little, too great a heating load will be thrown on the exhausting vapor stream, and it will be found impossible to eliminate all of the desired light material fractions from the residual liquid. The error on the side of heating the feed too high wastes heat, but the error on the side of heating the feed too low destroys the distillation efficiency of the system.

If the system is started up with too cold a feed, desired light material fractions will be found in the residual liquid. The first, and natural, move toward correcting this defect in quality would be to fire the exhausting heaters harder. Up to a certain critical point, the raising of the temperature at the exhausting heaters would raise the temperature of the exhausting column bottoms and de crease the light material content of the residual liquid; beyond this point, however, the system would simply overloadwith recycling exhausting vapors with no apparent improvement in quality of the residual material. When this vapor overloading finally occurs, it is then perfectly obvious that the feed temperature is too low. It is not necessary, however, to fire the exhausting heaters to such an extent in order to test out the correctness of any given feed temperature, since the real test for correctness of feed temperature lies in the character and magnitude of the gap between the feed temperature and the temperature of the vapors immediately above the feed plate-the system, of course, having first come to an equilibrium with the fractionating columns cutting the desired end point on the overhead products. Under certain conditions, the process will work satisfactorily with a feed temperature somewhat lower than that of the vapors, sometimes as much as 75 F., the exact value for this permissible temperature depression varying with. each type of feed and character of overhead products. In other cases, a feed temperature depression of aslittle as 25 F. will make it impossible to clear the residual liquid of all of the desired overhead fractions. Likewise, the feed temperature may under certain conditions be considerably higher than the corresponding vapor temperature, although a temperature which is materially elevated above that of the vapors will always require excessive refluxing. The optimum of correct feed temperature is attained when the feed and corresponding vapor temperatures are exactly the same.

Since a feed temperature depression of only a-few degrees may in some cases seri ously impair the distillation efliciency of the process, it is deemed good opera-ting practice to carry the feed temperature 2 to 10 F. higher than the corresponding vapor 'temperature. This elevation of feed temperature is so small that its effect on the thermal eiiiciency of the process'is negligible; at the same time it insures the achievement of a maximum distillation efiiciency.

In general, it may be stated that, the larger the percentage of cuts being taken oft, the less will be the permissible feed temperature depression below the optimum. For example, a 25% cut of gasoline may be successfully made from a certain California crude oil with a feed temperature depression of 60 F., yet when an additional 15% of kerosene distillate is desired (making a total of 40% overhead) this temperature depression must be reduced to approximately 10 F. On the other hand, the feed may always be heated higher than the optimum at the expense of thermal efiiciency only.

Many oil distillation systems make use of a feed material which has been heated in a more or less haphazard degree the primary object of such'heating residing in the desire to reclaim waste heat from residual products leaving the system. While this process by no means overlooks the economies resulting from such a heat conservation efi'ect, it goes much farther in recognizing the, absolute necessity of controlling the temperature of the feed material within very definite temperature limits (these limits varying, of course, with each particular type of feed material and character of overhead product) for the primary purpose of efi'ecting an economical In this process, the vapors generated by the heating of the exhausting column bottoms are released in a vapor separator apart from the heating elements of the exhausting heater. This separation of the exhausting vapors subsequent to their evolution ofier the following advantages 1. The temperature difierence between the exhausting column bottoms and the residual liquid in the vapor separator often amounts to 100150 F. By heating the exhausting column bottoms in counter-current contact with the heating medium, this temperature difference may be utilized to produce correspondingly lower exit temperatures of the heating medium (flue gases for example) with a corresponding increase in heating eficlency. n

2. The heating of the exhausting column bottoms previous to the releasing of the evolved vapors makes it possible to use a tubular construction for the exhausting heaterresulting in high capacity, high fuel efficiency economies common to all tubular heater installations. In addition, the use such a tubular heater also makes it possi le to operate the exhausting unit at high temperatures without encountering local overheating troubles.

3. In many distillation operations of the process, the exit temperatures carried on the residual liquid are at or just under the incipient cracking temperature.

Under such circumstances, if a portion of the residual material was recycled and held.

at this temperature, it would gradually break down. With the once-thorough heating, however, the period of time during which the residual material is held at its maximum tem erature is so short that no noticeable crac ing occurs.

4. Samples for determining the quality of materialsbeing made in the exhaustin col-' umn or vapor separator are immediately available for control purposes.

5. Changes'in the exhausting control of the process can be very quickly and easily made due to the small volume of liquid carried in the apparatus.

6. The control on the exhausting heater can be automatically maintained.

The primary duty of the exhausting column, as above mentioned, is to denude the original feed'material of such a proportion desired light fractions will be eliminated from the residual material at the exhausting va or separator. The elimination of these lig t fractions from the residual material requires the presence of comparatively heavy equilibrium vapors within the vapor separator. If these equilibrium vapors should contain any substantial amount of light tractions, a portion of the same would remain in the liquid, and the desired sharp out between overhead and bottoms would be lost. Obviously, then, if any substantial amount of cracking occurs at the exhausting heater, light cracked fractions will be present in the exhausting vapor separator, to the detriment of the residual liquid specifications. In addition, it should be noted that this process is specifically and solely a distillation process developed for the purpose of sharply separating various oil fractions originally held in solution with each other within a single feed material. For these reasons, the process is always operated in such a manner as to eliminate, to the best of the operators knowledge, all tendencies toward cracking at the exhausting units.

As previously indicated, the efiective 0per-.

ation of the process requires the use of the exhausting heating units in conjunction with exhausting and fractionating columns. In operating such a system, ust sufiicient reflux is'used at the fractionating'columns to give the desired end point and sharpness of fractionation to the overhead cuts, the temperature of the feed to the exhausting column is held at approximately that of the vapors above the feed plate, and the exhausting heaters are fired at the lowest permissible temperatures yielding the desired residual materialcut. Obviously, when starting up a unit, when the character of the feed material changes, or when a change is desired in the characterIof the distillation products, the control on the system must be adjusted until the above balance is obtained. It is during these periods of adjustment of control' that the described elimination of the storage of any appreciable volumes of oil within the *5 system is most keenly appreciated.

After establishing a preliminary temperature adjustment of the system, if large bodies of oil were held at the base of the rectifying columns and exhausting vaporizer, the unit would have to be operated for a considerable period of time to allow these bodies of material to come to equilibrium under the new temperature conditions; then test samples would be taken, the control readjusted, and another period of waiting gone through with while the bodies of oil agam'came to another equilibrium. With such an operation, many hours would elapse before the system could be brought into correct operating control, with a consequent large production of ofi specification materials and loss of efi'ective operating time. Although such a procedure appears absurd, in light of the obvious fact that representative samples of the new tem-I tion with a simple fractionating column.

Even the most casual comparison should readily reveal the superiority of the once through, tubular heated, non-storage features of the disclosed process as contrasted with the long time heating contact, shell fired, large storage features of the typical column fed shell unit. In addition to the time and material savings indicated above, the elimination of the storage 'of any appreciable bodies of oil within the system materially increases the sensitiveness of the same to slight temperature changes on the part of either vapors or liquid. This sensitiveness to temperature variation makes it possible to automatically control the character of the distillation products within very close specification limits.

As a result of this process, the heavy residual cuts obtained from the vapor separamediate distillate of 348 A. P. I. was introduced on the feed plate 5 in tower E at a temperature of 425 F., this temperature being two degrees higher than the temperature of the vapors immediately above said plate. The vapors withdrawn through the line 22 at the top of said tower E had a temperature of 395 F. while those discharged from the reflux condenser 23 to the condenser C had a temperature of 365 F. The bottoms were withdrawn from the chamber 9 at the bottom of the column E at a temperature of 480 F. and a gravity of 356 AQP. I. These bottoms after being heated in a tubular exhausting heater H were introduced at a temperature of 560 F. into the separator S from which vapors at 535 F. were introduced into the'chamber 9 of said column E. The residual material withdrawn from the bottom of separator S through the line 19 had a temperature of 547 and a'gravity of 335 A. P. I. The gasoline recovered from condenser C which had a gravity of 44 A. P. I. and constituted 11.8% out of a possible 12% of the original feed, had an end point by the standard Engler distillation test of 444 F.; while the 88.2% of residual material of the shown in Fig. 4 wherein the temperature of the vapors above said plate was approxi-' mately 430 F. Vapors were withdrawn from the top .of column E and introduced into the base of the column B at 425 F. while the vapors withdrawn through line 32 had a temperature of 360 F. The gasoline from these vapors amounted to 20% of the feed material and had a gravity of'54 A. P. I. The bottoms were withdrawn from the chamher 9 in the base of column E at a temperature of 475 F. and were elevated in the heater H to a temperature of 590 F. at which temperature they were introduced into the vapor separator S. The separated vapors withdrawn from the separator S were introduced into the chamber 9 at a temperature of 585 F. The residual material withdrawn from the base of separator S had a gravity of 171 A. P. I. and represented 78% of the feed. The water content of the feed was 1% and the loss resulting in the operation of the process was'1%. The end point of the gasoline recovered as a composite from the lines 36 and was 420 F, and the initial of the residual 35 material from the separator S was 430 F.

Thus, in this case, wherein a crude material was treated, the gap between the residual and overhead cuts was 10, F.

From these examples, it may be readily seen that very sharp cuts showing absolutely no overlap by the Engler test may be obtained by the present process.

I claim:

1. A method for the fractional distillation oil and introducing the same into an exhausting column in which lighter constituents are liberated, the temperature of ,the oil approximating that of the vapors in the column at the'point of introduction of the oil, passing heated vapors through said column for the purpose of releasing lighter constituents therefrom, withdrawing the bottoms. from said column and heating without cracking the same by a once-.throufgh'passage ina coil to generate a quantity 0 vapors, separating said vapors and employing thesame as said heated vapors for passage through said column to release said light constituents.

of petroleum oils comprising preheating an oil approximately to a definitely predetermined elevated temperature and introducing the same into a rectifying column in which lighter constituents are liberated, passdrawing the bottoms from said column and,

by a once-through passage in a coil, heating, the same without cracking to generatea quantity of hot distilling vapdrs, separating said hot vapors and-employing the same as those 7 relatively hotter vapors which are used to release lighter constituents.

3'. A method for the fractional distillation of. petroleum oils comprising preheating an oil and introducing the same into an exhausting column in which light constituents are liberated in the form'of vapo'rs, the temperature of the oil approximating thatof the vapors in the column at the point of introduction of the oil, withdrawing the bottoms from said column, heating without cracking the same by a once-through passage in a coil to generate a quantity of hot distilling vapors, separating said hot vapors and passing the same through said column countercurrently to the movement of the oil for the purpose of releasing lighter constituents therefrom. I? 4. A method for the fractional distillation of petroleum oils comprising preheating the oil, introducing'the preheated oil into a column in which vapors are liberated, said col-v umn having an exhausting section below the point of introduction of the oil and a washing section above the point of introduction of the oil, the temperature of the oil approximating that of the vapors in the column at the point of introduction of the oil, withdrawing the bottoms from the base of said column, heating without cracking the same by a once-through passage in a coil to generate a quantity of hot distilling vapors, separating said hot vapors from the residual material and passing the vapors so separated up through said exhausting section for the purpose or liheratin lighter constituents from the introduced oi 5. A method for the fractional distillation of petroleum oils comprising preheating'an 3110 oil, introducing the same .into an exhausting column in which the lighter constituents are liberated therefrom, the temperature of the oil. closely approximating that of Va ors in the exhausting column, at the point 0 introduction of the oil whereby the lightest constituents are liberated at said point of introduction, rectifying liberated vapors beyond said column and returning the reflux tothe upper portion of the column, withdrawing the bottoms from the base of the column and heating without cracking the same by a oncethrough passage in a coil to generate a quantity of hot distilling vapors, separating said 2. A method for the fractional distillation vapors from the residual material and passing said hot vapors up through said column for the liberation of lighter constituents from the oil flowing down through the-column.

6. A method for fractionally distilling petroleum oils for the purpose of obtaining a 8 I 1,soe,oas

sharp out between a relatively heavy residual product and a relatively light overhead product, comprising preheating an oil, introducing the same into a distillin column above an exhausting section thereo wherein light constituents of the oil are liberated, allowing the oil to descend through said exhausting section while in intimate countercurrent contact with an ascending stream of relatively hotter vapors for the purpose of further removing light constituents, withdrawing the resultant liquid bottoms from 'the base of the column, heating without cracking the bottoms by a once-through passage in a coil to generate the aforementioned vapors, separat ing the vapors from the remaining residual liquid at a place apart from the place of heat ing, returning the separated vapors to the base of the exhausting section of the distilling column to serve as said relatively hotter vapors, removing the residual liquid from the system, said liquid constituting the desired heavy residual product, introducing the vapors arising from the exhausting section above the point of oil introduction into a fractioning section, washing and fractioning these vapors to remove the undesirable heavy fractions entrained and evaporated in the exhausting section by bringing them into intimate countercurrent contact with a relatively colder reflux liquid introduced into the top of the fractionating section, feeding the bot-toms from the fractionating section, into the upper portion of the exhausting section, withdrawing the vapors from the top of the fractionating section and condensing them to 'form the desired light overhead product.

7. A method for the fractional distillation of petroleum oils, comprising preheating an 40 oil approximately to a definitely predetermined elevated temperature and introducing the same into a rectifying column in which lighter constituents are liberated, passing hot distilling vapors through said column for the 5 purpose of releasing lighter constituents and all the lightest constituents, withdrawing the bottoms from said column and, by a oncethrough passage in a coil, heating said bottoms without cracking to generate a quantity of hot distilling vapors, separatingthe'liquid portions of said bottoms from said hot vapors, removing said liquid portions from the system without recycling the same to the coil, and employing said separated hot vapors as the hot distilling vapors which are used to release said lighter constituents.

Signed at Los'Angeles, in the county of Los Angeles and State of California, this 1st day of November, A. D. 1926. EDWARD G. RAGATZ. 

